cm:Concept: us-gaap:DebtSecuritiesHeldToMaturityMaturityAfterFiveThroughTenYearsWeightedAverageYield
| Debt Securities, Held-to-maturity, Maturity, after Five Through Ten Years, Weighted Average Yield |
| us-gaap:DebtSecuritiesHeldToMaturityMaturityAfterFiveThroughTenYearsWeightedAverageYield |
| Weighted average yield of investment in debt security measured at amortized cost (held-to-maturity), maturing in sixth through tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. |
| cm:Concept |
| Percent (num:percentItemType) |
| As Of (instant) |
| (no balance type) |
| false |
| us-gaap:DebtSecuritiesHeldToMaturityMaturityAfterFiveThroughTenYearsWeightedAverageYield |